1. Field of the Invention
This invention relates to twisting technology for electric cables and wires and deals with the mechanical design of a twisting machine with a view toward obtaining a length of lay as uniform as possible, especially in the vicinity of the reversal points of the twist direction.
2. Description of the Prior Art
In SZ twisting of stranding elements of electric cables and wires by means of revolving twisting devices which change their rotary motion at intervals, the quality of the SZ twist (no tumbling of conductors, uniform length of lay in the vicinity of the reversal points of the twist direction, short reveral spots) depends essentially on the magnitude of the distances of fixed points, between which the twisting processes take place, and on the reversal times for changing the rotary motion of the revolving parts. The distances between the fixed points are very large, for instance, in SZ twisting machines which operate with stationary concentrated accumulators and revolving twisting heads (German Patent No. 16 65 536, DE-OS No. 16 65 911, DE-OS No. 16 85 842), but are very small in SZ twisting machines with unconcentrated longitudinal accumulators, so-called linear accumulators or straight accumulators (journal "Drahtwelt", 1977, pages 209 to 212). In unconcentrated longitudinal accumulators, the mentioned reversal times are very small, but the storage capacity in such storage devices is also relatively small. In rotating concentrated longitudinal accumulators, on the other hand, relatively long reversal times are obtained especially if the storage capacity is chosen to be very large (DE-AS 15 15 730).
Short reversal times in the SZ twisting of twist elements can also be achieved if the twisting is not accomplished by means of concentrated or unconcentrated longitudinal accumulators, in which the resulting twisting of the twisted material is obtained from the super-position of a first and at least one second twist, but by means of an oscillating twisting disc, which is optionally preceded by an equalization section (DE-OS No. 24 54 777).
To improve the quality of SZ twisting (especially the elimination of conductor tumbling), it is already known to arrange a hole disc (rotating or oscillating lay plate) through which the twisted twist elements pass after the SZ twisting machine. This hole disc untwists the twist elements and retwists them immediately. The rotary motion of this retwisting disc is either brought about by the twist elements themselves, or the retwisting disc is driven, at least briefly, when the twist direction changes. If, however, the retwisting disc is driven continuously at constant speed with the same running time in the one or the other direction as the twisting devices, automatic equalization of different lengths of lay, which are caused by the fact that for changing the direction of rotation of the twisting device, the latter must be braked to zero and subsequently accelerated again to the maximum speed, can be accomplished (DS-OS No. 25 10 643, DE-AS No. 16 65 552, DE-OS No. 22 02 643, DE-OS No. 24 12 514).